android - 包的开发人员警告，未能在 channel null 上发布通知，请参阅日志以获取更多详细信息。 toast

Question

我是我的 mp3 播放器。

它正在工作，但我总是收到一条 toast 消息

在此处输入图像描述



所以我想我需要在我的代码中通知 channel 。

但我不知道如何添加代码。帮我 !!

这是我的代码

public class MusicController extends MediaController {

public MusicController(Context c){
    super(c);
}

public void hide(){}
}

public class MusicService extends Service implements
    MediaPlayer.OnPreparedListener, MediaPlayer.OnErrorListener,
    MediaPlayer.OnCompletionListener {

//media player
private MediaPlayer player;
//song list
private ArrayList<Song> songs;
//current position
private int songPosn;
//binder
private final IBinder musicBind = new MusicBinder();
//title of current song
private String songTitle="";
//notification id
private static final int NOTIFY_ID=1;
//shuffle flag and random
private boolean shuffle=false;
private Random rand;

public void onCreate(){
    //create the service
    super.onCreate();
    //initialize position
    songPosn=0;
    //random
    rand=new Random();
    //create player
    player = new MediaPlayer();
    //initialize
    initMusicPlayer();
}

public void initMusicPlayer(){
    //set player properties
    player.setWakeMode(getApplicationContext(),
            PowerManager.PARTIAL_WAKE_LOCK);
    player.setAudioStreamType(AudioManager.STREAM_MUSIC);
    //set listeners
    player.setOnPreparedListener(this);
    player.setOnCompletionListener(this);
    player.setOnErrorListener(this);
}

//pass song list
public void setList(ArrayList<Song> theSongs){
    songs=theSongs;
}

//binder
public class MusicBinder extends Binder {
    MusicService getService() {
        return MusicService.this;
    }
}

//activity will bind to service
@Override
public IBinder onBind(Intent intent) {
    return musicBind;
}

//release resources when unbind
@Override
public boolean onUnbind(Intent intent){
    player.stop();
    player.release();
    return false;
}

//play a song
public void playSong(){
    //play
    player.reset();
    //get song
    Song playSong = songs.get(songPosn);
    //get title
    songTitle=playSong.getTitle();
    //get id
    long currSong = playSong.getID();
    //set uri
    Uri trackUri = ContentUris.withAppendedId(
            android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
            currSong);
    //set the data source
    try{
        player.setDataSource(getApplicationContext(), trackUri);
    }
    catch(Exception e){
        Log.e("MUSIC SERVICE", "Error setting data source", e);
    }
    player.prepareAsync();
}

//set the song
public void setSong(int songIndex){
    songPosn=songIndex;
}

@Override
public void onCompletion(MediaPlayer mp) {
    //check if playback has reached the end of a track
    if(player.getCurrentPosition()>0){
        mp.reset();
        playNext();
    }
}

@Override
public boolean onError(MediaPlayer mp, int what, int extra) {
    Log.v("MUSIC PLAYER", "Playback Error");
    mp.reset();
    return false;
}

@Override
public void onPrepared(MediaPlayer mp) {
    //start playback
    mp.start();
    //notification
    Intent notIntent = new Intent(this, MainActivity.class);
    notIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
    PendingIntent pendInt = PendingIntent.getActivity(this, 0,
            notIntent, PendingIntent.FLAG_UPDATE_CURRENT);

    Notification.Builder builder = new Notification.Builder(this);

    builder.setContentIntent(pendInt)
            .setSmallIcon(R.drawable.android_music_player_play)
            .setTicker(songTitle)
            .setOngoing(true)
            .setContentTitle("Playing")
            .setContentText(songTitle);
    Notification not = builder.build();
    startForeground(NOTIFY_ID, not);
}

//playback methods
public int getPosn(){
    return player.getCurrentPosition();
}

public int getDur(){
    return player.getDuration();
}

public boolean isPng(){
    return player.isPlaying();
}

public void pausePlayer(){
    player.pause();
}

public void seek(int posn){
    player.seekTo(posn);
}

public void go(){
    player.start();
}

//skip to previous track
public void playPrev(){
    songPosn--;
    if(songPosn<0) songPosn=songs.size()-1;
    playSong();
}

//skip to next
public void playNext(){
    if(shuffle){
        int newSong = songPosn;
        while(newSong==songPosn){
            newSong=rand.nextInt(songs.size());
        }
        songPosn=newSong;
    }
    else{
        songPosn++;
        if(songPosn>=songs.size()) songPosn=0;
    }
    playSong();
}

@Override
public void onDestroy() {
    stopForeground(true);
}

//toggle shuffle
public void setShuffle(){
    if(shuffle) shuffle=false;
    else shuffle=true;
}

}

public class MainActivity extends Activity implements MediaPlayerControl {

//song list variables
private ArrayList<Song> songList;
private ListView songView;

//service
private MusicService musicSrv;
private Intent playIntent;
//binding
private boolean musicBound=false;

//controller
private MusicController controller;

//activity and playback pause flags
private boolean paused=false, playbackPaused=false;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
        if (checkSelfPermission(Manifest.permission.READ_EXTERNAL_STORAGE)
                != PackageManager.PERMISSION_GRANTED) {

            requestPermissions(new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},1);


            return;
        }}

    //retrieve list view
    songView = (ListView)findViewById(R.id.song_list);
    //instantiate list
    songList = new ArrayList<Song>();
    //get songs from device
    getSongList();
    //sort alphabetically by title
    Collections.sort(songList, new Comparator<Song>(){
        public int compare(Song a, Song b){
            return a.getTitle().compareTo(b.getTitle());
        }
    });
    //create and set adapter
    SongAdapter songAdt = new SongAdapter(this, songList);
    songView.setAdapter(songAdt);

    //setup controller
    setController();
}

//connect to the service
private ServiceConnection musicConnection = new ServiceConnection(){

    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
        MusicBinder binder = (MusicBinder)service;
        //get service
        musicSrv = binder.getService();
        //pass list
        musicSrv.setList(songList);
        musicBound = true;
    }

    @Override
    public void onServiceDisconnected(ComponentName name) {
        musicBound = false;
    }
};

//start and bind the service when the activity starts
@Override
protected void onStart() {
    super.onStart();
    if(playIntent==null){
        playIntent = new Intent(this, MusicService.class);
        bindService(playIntent, musicConnection, Context.BIND_AUTO_CREATE);
        startService(playIntent);
    }
}

//user song select
public void songPicked(View view){
    musicSrv.setSong(Integer.parseInt(view.getTag().toString()));
    musicSrv.playSong();
    if(playbackPaused){
        setController();
        playbackPaused=false;
    }
    controller.show(0);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    //menu item selected
    switch (item.getItemId()) {
        case R.id.action_shuffle:
            musicSrv.setShuffle();
            break;
        case R.id.action_end:
            stopService(playIntent);
            musicSrv=null;
            System.exit(0);
            break;
    }
    return super.onOptionsItemSelected(item);
}

//method to retrieve song info from device
public void getSongList(){
    //query external audio
    ContentResolver musicResolver = getContentResolver();
    Uri musicUri = android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
    Cursor musicCursor = musicResolver.query(musicUri, null, null, null, null);
    //iterate over results if valid
    if(musicCursor!=null && musicCursor.moveToFirst()){
        //get columns
        int titleColumn = musicCursor.getColumnIndex
                (android.provider.MediaStore.Audio.Media.TITLE);
        int idColumn = musicCursor.getColumnIndex
                (android.provider.MediaStore.Audio.Media._ID);
        int artistColumn = musicCursor.getColumnIndex
                (android.provider.MediaStore.Audio.Media.ARTIST);
        //add songs to list
        do {
            long thisId = musicCursor.getLong(idColumn);
            String thisTitle = musicCursor.getString(titleColumn);
            String thisArtist = musicCursor.getString(artistColumn);
            songList.add(new Song(thisId, thisTitle, thisArtist));
        }
        while (musicCursor.moveToNext());
    }
}

@Override
public boolean canPause() {
    return true;
}

@Override
public boolean canSeekBackward() {
    return true;
}

@Override
public boolean canSeekForward() {
    return true;
}

@Override
public int getAudioSessionId() {
    return 0;
}

@Override
public int getBufferPercentage() {
    return 0;
}

@Override
public int getCurrentPosition() {
    if(musicSrv!=null && musicBound && musicSrv.isPng())
        return musicSrv.getPosn();
    else return 0;
}

@Override
public int getDuration() {
    if(musicSrv!=null && musicBound && musicSrv.isPng())
        return musicSrv.getDur();
    else return 0;
}

@Override
public boolean isPlaying() {
    if(musicSrv!=null && musicBound)
        return musicSrv.isPng();
    return false;
}

@Override
public void pause() {
    playbackPaused=true;
    musicSrv.pausePlayer();
}

@Override
public void seekTo(int pos) {
    musicSrv.seek(pos);
}

@Override
public void start() {
    musicSrv.go();
}

//set the controller up
private void setController(){
    controller = new MusicController(this);
    //set previous and next button listeners
    controller.setPrevNextListeners(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            playNext();
        }
    }, new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            playPrev();
        }
    });
    //set and show
    controller.setMediaPlayer(this);
    controller.setAnchorView(findViewById(R.id.song_list));
    controller.setEnabled(true);
}

private void playNext(){
    musicSrv.playNext();
    if(playbackPaused){
        setController();
        playbackPaused=false;
    }
    controller.show(0);
}

private void playPrev(){
    musicSrv.playPrev();
    if(playbackPaused){
        setController();
        playbackPaused=false;
    }
    controller.show(0);
}

@Override
protected void onPause(){
    super.onPause();
    paused=true;
}

@Override
protected void onResume(){
    super.onResume();
    if(paused){
        setController();
        paused=false;
    }
}

@Override
protected void onStop() {
    controller.hide();
    super.onStop();
}

@Override
protected void onDestroy() {
    stopService(playIntent);
    musicSrv=null;
    super.onDestroy();
   }
}

我该如何解决？ !帮我 !

Answer 1

根据 Migration MediaStyle notifications to support Android O blog post :

In order to use notifications in O, you must use notification channels.

如果您以 API 26 或更高版本为目标，则必须向所有通知添加通知 channel 。该博客文章介绍了您应该用于媒体通知的建议设置。